Growth performance and biomass production of Andropogon gayanus, Brachiaria falcifera, and Hyparrhenia smithiana under water deficit conditions

Increasing rainfall variability and recurrent droughts associated with climate change threaten the productivity and stability of West African rangelands, which support livestock production and rural livelihoods. Identifying forage species with adaptive responses to water limitation is therefore important for improving the resilience of forage systems. This study evaluated the effects of water deficit on the growth and biomass production of Andropogon gayanus , Brachiaria falcifera , and Hyparrhenia smithiana under greenhouse conditions in Benin. A factorial experiment was conducted using three species and four water regimes (100%, 75%, 50%, and 25% field capacity). Plant height, collar diameter, tiller production, and aboveground and belowground biomass was measured. Results showed species-specific responses to water deficit. Plant height remained relatively stable in the three species across treatments, although B. falcifera showed a slight reduction under severe water deficit. Collar diameter increased under moderate water deficit in A. gayanus , decreased in B. falcifera , and remained relatively stable in H. smithiana . Tiller production was the most consistently responsive growth trait across the three species. Biomass production declined significantly in A. gayanus , remained relatively stable in B. falcifera , and was mainly affected in the belowground fraction of H. smithiana . The shoot-to-root biomass ratio varied significantly among water treatments in all three species. These contrasting responses suggest that A. gayanus and H. smithiana exhibit potentially useful adaptive traits under water limitation. This provides a scientific basis for selecting forage species that can enhance the long-term sustainability of West African rangelands under increasing climate variability.